Definitions for wadsleyite

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wadsleyite(Noun)

An orthorhombic form of olivine produced under very high pressure

Origin: named after geologist Dr. Arthur David Wadsley.

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Wadsleyite

Wadsleyite is a high-pressure polymorph of olivine, and is an orthorhombic mineral found in the Peace River meteorite in Alberta, Canada. In phase transformations with increasing pressure from Mg2SiO4-Fe2SiO4, olivine is transformed to wadsleyite and then to a spinel-structured ringwoodite. This series of transformations is thought to occur during an extraterrestrial shock event in the meteorite prior to its fall on Earth. With a formula of (Mg,Fe²+)2, its cell parameters are as follows: a = 5.7 Å, b = 11.7 Å and c = 8.24 Å. It is polymorphous with ringwoodite and is found to be stable in the transition zone of the Earth’s upper mantle. These regions are from 400–525 kilometres in depth. Because of oxygens not bound to silicon in the Si2O7 groups of wadsleyite, it leaves some oxygen atoms underbonded, and as a result, these oxygens are hydrated easily. As a result, there can be high concentrations of hydrogen atoms in the mineral. Hydrous wadsleyite is a considered a potential site for water storage in the Earth’s mantle due to the low electrostatic potential of the underbonded oxygen atoms. Although wadsleyite does not contain H in its chemical formula, it may contain more that 3 percent by weight H2O, and may coexist with a hydrous melt at transition zone pressure-temperature conditions. The water solubility and density of wadsleyite are ultimately affected by the temperature and pressure inside of the Earth.